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Microstructure, thermal stability and mechanical properties of slowly cooled Zr-based composites containing dendritic bcc phase precipitates

Published online by Cambridge University Press:  01 February 2011

Nicolle Radtke
Affiliation:
IFW Dresden, Institute of Metallic Materials, P.O. Box 270016, D-01171 Dresden, Germany
Jürgen Eckert
Affiliation:
TU Darmstadt, Institut of Material Science, Petersenstr. 23, D-64287 Darmstadt, Germany
Uta Kühn
Affiliation:
IFW Dresden, Institute of Metallic Materials, P.O. Box 270016, D-01171 Dresden, Germany
Mihai Stoica
Affiliation:
IFW Dresden, Institute of Metallic Materials, P.O. Box 270016, D-01171 Dresden, Germany
Ludwig Schultz
Affiliation:
IFW Dresden, Institute of Metallic Materials, P.O. Box 270016, D-01171 Dresden, Germany
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Abstract

We report on the microstructure, the thermal stability and the mechanical properties of slowly cooled Zr-Nb-Cu-Ni-Al alloys with ductile bcc phase precipitates embedded in a glassy or nanocrystalline matrix. The samples were prepared in form of rods by injection casting into a copper mold. The phase formation and the microstructure of the composite material were investigated by X-ray diffraction, EDX analysis and scanning and transmission electron microscopy. The thermal stability was examined by differential scanning calorimetry and the mechanical behavior was investigated by compression tests under quasistatic loading at room temperature. The formation of bcc phase dendrites and a glassy or nanocrystalline matrix is strongly governed by the alloy composition and the actual cooling rate during solidification. Besides, changes in composition and cooling rate lead to different volume fraction and size of the bcc phase precipitates and, hence, to different values of yield strength, elastic and plastic strain. The samples with nanocrystalline matrix show a homogeneous distribution of the bcc phase precipitates over the whole cross-section and exhibit higher yield strength and plastic strain than the samples containing an amorphous matrix. Illustrated by the presented results we show the possibility of obtaining tailored mechanical properties by control of composition and solidification conditions.

Type
Research Article
Copyright
Copyright © Materials Research Society 2004

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References

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